U.S. patent application number 14/564547 was filed with the patent office on 2015-06-11 for oxygen scavenger for drilling fluids.
The applicant listed for this patent is CANADIAN ENERGY SERVICES L.P.. Invention is credited to Jonathan Robert HALE.
Application Number | 20150159072 14/564547 |
Document ID | / |
Family ID | 53270516 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150159072 |
Kind Code |
A1 |
HALE; Jonathan Robert |
June 11, 2015 |
OXYGEN SCAVENGER FOR DRILLING FLUIDS
Abstract
There is provided the use of alkylhydroxylamines (AHA), and in
particular, N,N-diethylhydroxylamine (DEHA), as an oxygen scavenger
for reducing free dissolved oxygen in drilling fluid which is
substantially free of erythorbate, erythorbic acid, or
stereoisomers thereof. The AHA may be used to reduce the free
dissolved oxygen in order to reduce undesirable corrosion or
degradation caused by free dissolved oxygen. The AHA may be
combined with a suitable diluent and/or antifreeze.
Inventors: |
HALE; Jonathan Robert;
(Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANADIAN ENERGY SERVICES L.P. |
Calgary |
|
CA |
|
|
Family ID: |
53270516 |
Appl. No.: |
14/564547 |
Filed: |
December 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61914173 |
Dec 10, 2013 |
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Current U.S.
Class: |
507/132 |
Current CPC
Class: |
C09K 2208/32 20130101;
C09K 8/06 20130101 |
International
Class: |
C09K 8/06 20060101
C09K008/06 |
Claims
1. A method of reducing dissolved oxygen in drilling fluid,
comprising adding an alkylhydroxylamine (AHA) to the drilling
fluid, wherein the drilling fluid is substantially free of
erythorbate, erythorbic acid, or a stereoisomer thereof.
2. The method of claim 1 wherein the drilling fluid is a brine
fluid.
3. The method of claim 2 where the AHA is N,N-diethylhydroxylamine
(DEHA).
4. The method of claim 1, wherein the AHA reduces the free
dissolved oxygen in the drilling fluid to 2 mg/L or less.
5. The method of claim 1, wherein the AHA reduces the free
dissolved oxygen in the drilling fluid to 2 mg/L or less within 30
minutes.
6. The method of claim 1, wherein the AHA holds the dissolved
oxygen in the drilling fluid to 2 mg/L or less for 72 hours.
7. The method of claim 1, wherein less than 20 kg/m.sup.3, or less
than 10 kg/m.sup.3, or less than 1 kg/m.sup.3, or less than 0.5
kg/m.sup.3, of the AHA is used.
8. The method of claim 1, wherein less than 12 L/m.sup.3, or less
than 6.0 L/m.sup.3, or less than 1.5 L/m.sup.3 of the AHA is
used.
9. The method of claim 1 wherein the AHA further comprises a
diluent, antifreeze or a catalyst.
10. The method of claim 9 wherein the catalyst is hydroquinone or
gallic acid.
11. The method of claim 9, wherein the antifreeze is selected from
the group consisting of methanol, ethanol, and ethylene glycol.
12. The method of claim 9, wherein the antifreeze is present in the
composition in an amount of 5 to 35%, or 10 to 30%, or 15 to 25%,
or about 16%, or about 20%, or about 24%, based on
volume/volume.
13. The method of claim 9, wherein the antifreeze is present in the
composition in an amount sufficient to yield a crystallization
point for the composition of -20.degree. C. or less, or -25.degree.
C. or less, or -30.degree. C. or less, or -35.degree. C. or less,
or -40.degree. C. or less.
14. The method of claim 1 wherein the drilling fluid is a brine
drilling fluid.
15. The method of claim 14, wherein the brine drilling fluid
comprises calcium salts.
16. The method of claim 14, wherein the brine drilling fluid is a
heavy brine.
17. A brine drilling fluid comprising an alkylhydroxylamine (AHA)
as an oxygen scavenger, wherein the drilling fluid is substantially
free of erythorbate, erythorbic acid, or a stereoisomer
thereof.
18. The brine drilling fluid of claim 17 wherein the AHA is
N,N-diethylhydroxylamine (DEHA).
19. The brine drilling fluid of claim 17 further comprising one or
more of a diluent, antifreeze, or a catalyst.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application No. 61/914,173 filed Dec. 10, 2013,
which is incorporated herein by reference in its entirety.
FIELD
[0002] The present disclosure relates generally to oxygen
scavengers for drilling fluids used in the recovery of oil and
gas.
BACKGROUND
[0003] Drilling fluids often contain dissolved and entrained air
which enters the fluids when its components are mixed and when the
fluid circulates through the drill string into the wellbore.
Dissolved oxygen and entrained air are undesirable in drilling
fluids. The presence of oxygen in the fluid drastically increases
the rate of corrosion and deterioration of metal surfaces in the
drill string, casing, and associated equipment as compared to
fluids which do not contain oxygen. This may manifest as general
oxidative attack, pitting, crevice corrosion, and/or under-deposit
corrosion. These are major factors in equipment failure.
[0004] Dissolved oxygen can also lead to free radical-based
decomposition of drilling fluid additives, particularly polymeric
additives.
[0005] To reduce dissolved oxygen, it is recommended that water be
added to drilling fluid and mixed as far from the main pump suction
as possible. Other physical adjustments can be made to the
circulation system to reduce air entrapment (see e.g. H. E. Bush
(1974), Treatment of Drilling Fluid to Combat Corrosion. Paper
Number SPE 5123, American Institute of Mining, Metallurgical, and
Petroleum Engineers). Adding water to hot mud allows the heat from
the mud to reduce the amount of dissolved oxygen in the cooler
water. However, dissolved oxygen still enters drilling fluid via
surface interfaces, despite precautions to reduce unnecessary
aeration.
[0006] Mechanical deaeration can be used to remove some bulk oxygen
from drilling fluids, but chemical additives are generally required
to achieve sufficiently low levels of dissolved oxygen required to
reduce corrosion and degradation. These chemical additives, termed
"oxygen scavengers", are generally reducing agents that are
oxidized by reacting with free dissolved oxygen. In doing so, the
oxygen scavenger chemically sequesters the dissolved oxygen so that
it is no longer available to cause undesirable corrosion or
degradation. Common oxygen scavengers including sulfites,
hydrazines, and erythorbates.
[0007] Drilling fluids are used in a variety of conditions such as
high pressure, high temperature environments, or shale which are
subject to swelling and absorption of the drilling fluid. These
environments require specialized fluids. Not all oxygen scavengers
are compatible or effective with drilling fluid environments.
[0008] Some oxygen scavengers are inactivated by heat, for example.
U.S. Patent Publication No. 2012/0118569 addresses the issue of the
heat labile nature of erythorbate in a completion fluid, and
describes methods of reducing dissolved oxygen in the completion
fluid using a blend of erythorbate and an alkylhydroxylamine,
wherein the alkylhydroxylamine stabilizes the erythorbate at high
temperatures. U.S. Patent Publication No. 2013/0178398 discloses
completion brines containing a blend of the same.
[0009] Some oxygen scavengers are not compatible with salts. Brines
are commonly used to prevent or reduce shale swelling in clay
formations but may also reduce the effectiveness of some oxygen
scavengers, such as sulfites.
[0010] Accordingly, there is a need for oxygen scavengers that are
compatible with drilling applications.
SUMMARY
[0011] It is an object of the present disclosure to obviate or
mitigate at least one disadvantage of previous approaches.
[0012] In one aspect, there is provided a use of an
alkylhydroxylamine as an oxygen scavenger in drilling fluid for
reducing dissolved oxygen in the fluid, wherein the drilling fluid
is substantially free of erythorbate, erythorbic acid, or a
stereoisomer thereof.
[0013] In another aspect, the alkylhydroxylamine may be used in
conjunction with a catalyst. The catalyst improves the oxygen
scavenging ability of the alkylhydroxylamine. Any catalyst suitable
for use with alkylhydroxylamine may be used and may include for
example hydroquinone and Gallic acid.
[0014] In another aspect, there is provided a use of a composition
comprising an alkylhydroxylamine and an acceptable diluent for
reducing dissolved oxygen in drilling fluid, wherein the drilling
is substantially free of erythorbate, erythorbic acid, or a
stereoisomer thereof.
[0015] In a further aspect, the alkylhydroxylamine is
N,N-diethylhydroxylamine (DEHA).
[0016] In a further aspect, the AHA is mixed with an
antifreeze.
[0017] In a further aspect, the drilling fluid is a brine. The
brine may comprise calcium salts. In a further aspect, the brine
drilling fluid is a heavy brine.
[0018] In one aspect, there is provided a method of reducing
dissolved oxygen in drilling fluid, comprising adding an AHA to
drilling fluid, wherein the drilling fluid is substantially free of
erythorbate, erythorbic acid, or a stereoisomer thereof. In one
embodiment, the step of adding may comprise adding the AHA as a
compound, as a composition mixed with a catalyst, as a composition
mixed with a diluent, or as a composition premixed with antifreeze,
with or without a catalyst or further diluent. In one embodiment,
the AHA may be DEHA.
[0019] Other aspects and features of the present disclosure will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments.
DETAILED DESCRIPTION
[0020] Generally, the present disclosure relates to the use of
alkylhydroxylamines as oxygen scavengers in drilling fluids and in
particular in brine fluids.
[0021] In one aspect, there is provided a use of
alkylhydroxylamines (AHA) for reducing dissolved oxygen in drilling
fluid, wherein the drilling fluid is substantially free of
erythorbate, erythorbic acid, or a stereoisomer thereof. The AHA
may be added into the drilling fluid as a compound, as a
composition mixed with a diluent, or as a composition mixed with
antifreeze, with or without further diluent.
[0022] The AHA when used as an oxygen scavenger reacts with and
sequesters free dissolved oxygen. This is desirable to prevent or
reduce corrosion (e.g. of metal parts), and/or to reduce
free-radical induced decomposition (e.g. of additives, such as
polymeric additives).
[0023] The AHA may be, for example, isopropylhydroxylamine,
diethylhydroxylamine (DEHA), tertbutylhydroxylamine,
phenylhydroxylamine, cyclohexylhydroxylamine, or
benzylhydroxylamine. Other suitable AHAs would be known to a
skilled person.
[0024] In one aspect, the alkylhydroxylamine is DEHA.
[0025] The AHA may be used to reduce the dissolved oxygen level to
preferred levels of 3 mg/L or less, 2 mg/L or less, 1 mg/L or less,
0.5 mg/L or less, or 0.25 mg/L or less. The AHA may be used to
reduce the dissolved oxygen level to 10 ppm or less. In one aspect,
the AHA is used for reducing the dissolved oxygen in the drilling
fluid to a level of 2 mg/L or less. These levels may be the levels
measured in fluid going downhole. A skilled person would be aware
of an acceptable level of dissolved oxygen that would be tolerable
in the drilling fluid dependent upon the intended application, and
could readily adjust the amount of AHA accordingly to achieve
this.
[0026] The AHA may be used to reduce dissolved oxygen to the
desired level within a desired time frame, such as within 30
minutes or less, 60 minutes or less, or 72 hours or less. In one
aspect, dissolved oxygen is reduced to the desired level in 30
minutes or less.
[0027] The AHA may also be used to hold dissolved oxygen at the
desired level for a desired period of time, such as for 30 minutes
or more, 60 minutes or more, or 72 hours or more. In one aspect,
dissolved oxygen is held at the desired level for at least 72
hours.
[0028] In other aspects, the AHA is used in the drilling fluid in
an amount of 20 kg/m.sup.3 or less, 10 kg/m.sup.3 or less, 5
kg/m.sup.3 or less, 1 kg/m.sup.3 or less, or 0.5 kg/m.sup.3 or
less.
[0029] It has been found in testing that usage may be below 12
L/m.sup.3. In one aspect, it may be below 6.0 L/m.sup.3 and in a
further aspect, may be below 1.5 L/ m.sup.3. One range of amount of
AHA is between 1.5-6.0 L/m.sup.3 but can be above or below this
range as required, depending on a number of factors including the
specific drilling fluid and formation.
[0030] The amount of AHA used will, in some embodiments, be
determined by the ability of the additive(s) to maintain
sufficiently low dissolved oxygen content in the drilling fluid
such that corrosion rates, (e.g. as monitored using corrosion rings
and in accordance with API RP 13B-1, Fourth Edition, March 2009,
Annex E) are maintained under 50 mpy. This will be achieved through
the use of AHA, one or more corrosion inhibitor(s), or a
combination of the two means of corrosion control. The acceptable
corrosion rate can be determined by application. The corrosion rate
may be 50 mpy, 40 mpy, 30 mpy, 25 mpy, 20 mpy, 15 mpy, 10 mpy, or 5
mpy. In some applications, a corrosion rates under 25 mpy may be
desirable.
[0031] The AHA may be added to the drilling fluid in combination
with a catalyst. The catalyst improves the oxygen scavenging
ability of the AHA. The catalyst may be any known catalyst that is
compatible with AHA and includes, for example, hydroquinone, gallic
acid, copper, benzoquinone, 1,2-naphthoquinone-4-sulfonic acid,
pyrogallol and t-butylcatechol. The amount of catalyst will depend
on the specific AHA and catalyst selected as well as the
composition of the drilling fluid. In one aspect, less than 1000
ppm of catalyst is added.
[0032] The drilling fluid may be of any conventional type which is
well known within the field. In one aspect, the drilling fluid is a
brine. Brines may be used for a number of reasons, such as to
increase density and/or to inhibit shale hydration and swelling. A
skilled person would be aware of brine fluids that would be
suitable for use as drilling fluids. In one aspect, the drilling
fluid is a heavy brine. In a further aspect, the brine comprises
calcium salts.
[0033] The drilling fluid may include conventional additives. These
may include surfactants, emulsifiers, fluid loss control additives,
biocides, high temperature stabilizers, and descalers. Other
potential additives include defoamers, viscosifiers, flocculating
polymers (to effectively reduce the solids content of the fluid),
lubricants (both liquid filming and solid ball-bearing type), LCM
(loss of circulation material), grouting and wellbore stability
additives, barite or calcium carbonate for weight in an unexpected
well control situation, pH or alkalinity control additives.
[0034] One particular additive that may be used in SC-202, which is
a scale control additive. SC-202 is a proprietary phosphonic acid
and alkylamine mixture. Its function is to control unwanted
precipitation of scales when brine fluids, especially those
containing calcium, mix with connate water.
[0035] In another aspect, there is provided a use of a composition
comprising an AHA, such as N,N-diethylhydroxylamine (DEHA), and an
acceptable diluent for reducing dissolved oxygen in drilling fluid,
wherein the drilling fluid is substantially free of erythorbate,
erythorbic acid, or a stereoisomer thereof. In one aspect, the
diluent may be water.
[0036] In a further aspect, the composition may include antifreeze.
The antifreeze may be any compound (or mixture thereof) with
suitable antifreeze properties, which is compatible with drilling
operations, and which does not greatly inhibit AHA oxygen
scavenging activity. The antifreeze may be selected based on
application and environmental factors, such as temperature at the
drilling site and composition of the drilling fluid. A skilled
person could readily select an appropriate antifreeze compound to
achieve a desired crystallization point for the drilling fluid, and
which would not inhibit oxygen scavenging activity of the AHA in
the drilling fluid. Examples of antifreeze including methanol,
ethanol, and ethylene glycol. The antifreeze may be used alone or
in combination with a suitable diluent such as water.
[0037] In one aspect, the composition contains antifreeze in an
amount of 5 to 35%, 10 to 30%, or 15 to 25%, based on
volume/volume. In certain aspects, the composition may comprise
about 16% antifreeze, about 20% antifreeze, or about 24%
antifreeze. By "about" is meant plus or minus 10%.
[0038] The amount of antifreeze would be adjusted for the specific
application, for example, depending on the season, or the
temperature at the drilling site. A skilled person could readily
select antifreeze amounts required to achieve a desired
crystallization point for the drilling fluid. In one aspect, the
antifreeze is present in an amount sufficient to yield a
crystallization point for the composition of -20.degree. C. or
less, 25.degree. C. or less, -30.degree. C. or less, -35.degree. C.
or less, or -40.degree. C. or less. In one aspect, the
crystallization point is about -40.degree. C.
[0039] In one specific embodiment, the composition comprises 15 to
20% by volume of an 85% DEHA solution, mixed with a sufficient
amount of ethylene glycol (e.g. provided as an 80:20 stock solution
by volume) to achieve a crystallization point of -40.degree. C. or
lower.
[0040] In one aspect, the antifreeze is mixed with water in a ratio
range of from 80:20 to 60:40. The specific range will depend on the
particular application and environmental factors for use of the
drilling fluid and appropriate ratios may fall outside this
range.
[0041] In one aspect, the drilling fluid is stable and
singled-phase after the composition is added. It may be stable and
single phase following one or more rounds of freezing and
thawing.
EXAMPLE 1
Preparation of Alkaline Brine
[0042] An alkaline brine was prepared to simulate the drilling
environment. 3 L of 30% CaCl.sub.2 brine was prepared as follows,
and allowed to cool to room temperature.
[0043] Approximately 4g of soda pearls was mixed in 100 mL of
water, and adjustments were made such that when a drop of this
alkaline solution was added to a sample of the 30% CaCl.sub.2
brine, no solid precipitate formed. The pH of the CaCl.sub.2 brine
solutions (measured with calibrated pH meter) was then raised to 10
to simulate the drilling fluid environment, by adding the alkaline
solution drop-wise while the brine was stirring. Density of the
alkaline brine was measured by use of a hydrometer, and found to be
1.246 kg/m3.
[0044] 250 mL Erlenmeyer flasks were labeled according to the
oxygene scavenger to be added, and appropriate amounts of the
descaling agent, SC-202, were added to the appropriate flasks
(except for negative controls), followed by 250 mL of brine (volume
measured by weight).
EXAMPLE 2
Test Data for Oxygen Scavengers
[0045] Each flask was equipped with a magnetic stirring rod,
stopper, and placed on a stir plate. Solutions began stirring at 2
minute intervals to create aeration and scavenger was added as
stirring began. The following oxygen scavengers were tested, one
per flask: N,N-diethylhydroxylamine (DEHA), uncatalyzed sodium
sulphite, sodium erythorbate, catalyzed sodium sulphite, and liquid
ammonium bisulphate (WO).
[0046] Testing with DEHA involved using an 85% stock solution as
the additive and the L/m.sup.3 units refer to this stock solution.
The density of this stock solution is about 0.9, kg/m.sup.3 .
[0047] Oxygen content of each solution was measured after 30, 60,
and 120 minutes, and at 17 hours. Stirring was ceased after 60
minutes.
[0048] Table 1 depicts oxygen saturation data for two control
samples, to which no scavenger was added in order to establish
baseline data.
TABLE-US-00001 TABLE 1 Control With SC-202 (2.5 L/m.sup.3) pH 9.8
Without SC-202 pH 10 [Oxygen] Temp [Oxygen] Temp Time (mg/L) .+-.
0.3 (.degree. C.) Time (mg/L) .+-. 0.3 (.degree. C.) 30 min 4.89
23.8 30 min 4.65 24.0 60 min 4.86 23.3 60 min 4.68 23.6 120 min
4.89 23.0 120 min 4.83 23.0 17 hrs 4.62 20.1 15 hrs 4.55 20.1
[0049] Table 2 depicts oxygen saturation data for
N,N-diethylhydroxylamine samples (30% CaCl.sub.2 pH 10) with and
without SC-202.
TABLE-US-00002 TABLE 2 N,N-diethylhydroxylamine (0.5 L/m.sup.3)
With SC-202 (2.5 L/m.sup.3)pH 9.9 Without SC-202 pH 10 [Oxygen]
Temp [Oxygen] Temp Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L)
.+-. 0.3 (.degree. C.) 30 min 0.25 24.1 30 min 0.26 23.4 60 min
0.31 23.8 60 min 0.40 22.9 120 min 0.38 23.1 120 min 0.40 22.6 17
hrs 0.21 20.8 15 hrs 0.31 20.1
[0050] As evidenced from this data, DEHA is compatible with the
SC-202 descaler, as its presence does not significantly impact the
oxygen scavenging ability of DEHA.
[0051] Table 3 depicts oxygen saturation data for sodium sulphite
samples (30% CaCl.sub.2 pH10).
TABLE-US-00003 TABLE 3 Sodium Sulphite (0.5 kg/m.sup.3) With SC-202
(2.5 L/m.sup.3) pH 9.9 Without SC-202 pH 10 [Oxygen] Temp [Oxygen]
Temp Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-. 0.3
(.degree. C.) 30 min 4.75 23.3 30 min 3.9 23.3 60 min 4.43 22.9 60
min 1.61 23.1 120 min 3.97 22.3 120 min 0.74 22.3 17 hrs 3.60 20.3
15 hrs 0.40 20.7
[0052] This data makes clear that the presence of SC-202 negatively
impact the oxygen scavenging ability of sodium sulphite.
[0053] Table 4 depicts oxygen saturation data for sodium
erythorbate samples (30% CaCl.sub.2 pH10).
TABLE-US-00004 TABLE 4 Sodium Erythorbate (0.5 kg/m.sup.3) With
SC-202 (2.5 L/m.sup.3) pH 9.9 Without SC-202 pH 10 [Oxygen] Temp
[Oxygen] Temp Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-.
0.3 (.degree. C.) 30 min 0.45 24.6 30 min 0.43 23.7 60 min 0.17
25.1 60 min 0.28 23.3 120 min 0.23 24.0 120 min 0.32 22.5 17 hrs
0.33 22.8 15 hrs 0.31 20.6
[0054] The presence of SC-202 does not appear to significantly
impact the oxygen scavenging activity of sodium erythorbate.
[0055] Table 5 presents oxygen saturation data for catalyzed sodium
sulphite samples (30% CaCl.sub.2 pH10).
TABLE-US-00005 TABLE 5 Catalyzed Sodium Sulphite (0.5 kg/m.sup.3)
With SC-202 (2.5 L/m.sup.3) Without SC-202 [Oxygen] Temp [Oxygen]
Temp Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-. 0.3
(.degree. C.) 30 min 4.43 22.5 30 min 3.01 22.7 60 min 4.20 23.0 60
min 2.93 23.1 120 min 4.19 24.1 120 min 2.45 24.1 17 hrs 4.02 23.0
15 hrs 1.90 23.0
[0056] As with uncatalyzed sodium sulphite, the presence of SC-202
significantly impacts the oxygen scavenging effectiveness of
catalyzed sodium sulphite
[0057] Table 6 presents oxygen saturation data for liquid ammonium
bisulphate (WO) samples (30% CaCl.sub.2 pH10).
TABLE-US-00006 TABLE 6 Liquid Ammonium Bisulphate (0.5 L/m.sup.3)
With SC-202 (2.5 L/m.sup.3) Without SC-202 [Oxygen] Temp [Oxygen]
Temp Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-. 0.3
(.degree. C.) 30 min 4.08 24.2 30 min 3.20 24.2 60 min 4.05 24.1 60
min 2.70 25.4 120 min 3.95 24.0 120 min 2.35 26.5 17 hrs 4.15 20.6
15 hrs 2.75 20.6
[0058] It is clear that liquid ammonium bisulphate is not
particular effective as an oxygen scavenger in calcium brine, with
or without SC-202 descaler.
EXAMPLE 3
Comparisons of Oxygen Scavengers
[0059] The following tables show comparisons of the effectiveness
of oxygen scavengers. The amounts tested in each case have been
selected with a cost basis in mind. For reference, sodium
erythorbate is roughly twice the cost of sodium sulphite; while an
85% DEHA stock solution is roughly 2.5 times the cost of sodium
sulphite.
[0060] Table 7 presents a comparison of the effectiveness of
uncatalyzed sodium sulphite and sodium erythorbate.
TABLE-US-00007 TABLE 7 1.5 kg/m.sup.3 uncatalyzed Sodium Sulphite
0.5 kg/m.sup.3 Sodium Erythorbate [Oxygen] Temp [Oxygen] Temp Time
(mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-. 0.3 (.degree. C.) 30
min 1.34 24.2 30 min 0.22 23.3 60 min 1.43 24.9 60 min 0.12 22.9
120 min 1.04 23.3 120 min 0.15 22.2 17 hrs 0.45 21.9 17 hrs 0.20
22.0
[0061] Sodium erythorbate is a more effective oxygen scavenger than
uncatalyzed sodium sulphite in calcium brine.
[0062] Table 8 presents a comparison of the effectiveness
uncatalyzed sodium sulphite and N,N-diethylhydroxylamine (DEHA).
Again, testing with DEHA involved using an 85% stock solution as
the additive.
TABLE-US-00008 TABLE 8 1.8 kg/m.sup.3 uncatalyzed Sodium Sulphite
0.5 L/m.sup.3 N,N-diethylhydroxylamine [Oxygen] Temp [Oxygen] Temp
Time (mg/L) .+-. 0.3 (.degree. C.) Time (mg/L) .+-. 0.3 (.degree.
C.) 30 min 1.30 23.8 30 min 0.23 23.5 60 min 1.05 23.4 60 min 0.18
23.6 120 min 0.33 22.4 120 min 0.16 22.9 17 hrs 0.38 21.8 17 hrs
0.22 21.9
[0063] DEHA is more effective as an oxygen scavenger than sodium
sulphite at all time points tested. DEHA also scavengers oxygen
much more quickly than sodium sulphite, as evidenced from the
greatly reduced oxygen levels at 30- and 60-minute time points.
[0064] Table 9 presents comparative data for certain oxygen
scavengers. The amounts tested have again been selected for
comparison based on cost.
[0065] 0.5 kg/m.sup.3 sodium sulphite was chosen based on field
usage. The 0.126 L/m.sup.3 of DEHA and 0.17 kg/m.sup.3 sodium
erythorbate were chosen to come in at slightly under the cost
(about 2/3 the cost) of the 0.5 kg/m.sup.3 sodium sulphite.
Finally, the lower amount of DEHA, 0.0378 L/m.sup.3, was a low
concentration found to just out-perform the sodium sulphite at 0.5
kg/m.sup.3, and hence provides an indication of how much DEHA is
required to match the performance of sodium sulphite.
TABLE-US-00009 TABLE 9 30 min 60 min 120 min 17 hrs [O.sub.2]
[O.sub.2] [O.sub.2] [O.sub.2] (mg/ Temp (mg/ Temp (mg/ Temp (mg/
Temp Additive L) (.degree. C.) L) (.degree. C.) L) (.degree. C.) L)
(.degree. C.) [0.5 kg/m.sup.3] 3.43 22.8 2.61 23.2 1.05 23.8 0.40
21.3 Sodium Sulphite [0.126 L/m.sup.3] 1.26 22.6 0.23 23.3 0.19
24.1 0.25 21.0 DEHA [0.0378 L/m.sup.3] 2.87 22.6 1.64 23.3 0.75
23.5 0.38 21.4 DEHA [0.17 kg/m.sup.32] 0.45 22.8 0.18 23.6 0.16
23.9 0.19 21.2 Sodium Erythorbate
[0066] Both amounts of DEHA were more effective at all time points
than a significantly larger quantity of sodium sulphite, reflective
of sodium sulphite's poor oxygen scavenging in calcium brines, and
DEHA's superior performance.
[0067] Although sodium erythorbate was most effective at the
30-minute time point, it is notable that a smaller amount of DEHA
(0.126 L/m.sup.3) was comparably effective at 60 minutes (0.23 mg/L
dissolved oxygen for DEHA vs. 0.18 mg/L for sodium erythorbate at
60 minutes) and 120 minutes (0.19 mg/L dissolved oxygen for DEHA
vs. 0.16 mg/L for sodium erythorbate at 120 minutes).
[0068] It is significant that an amount of DEHA that is about an
order of magnitude lower than that of sodium sulphite (0.0378
L/m.sup.3 DEHA vs. 0.5 kg/m.sup.3 sodium sulphite) worked better
than sodium sulphite at 120 minutes (0.75 mg/L dissolved oxygen for
DEHA vs. 1.05 mg/L dissolved oxygen for sodium sulphite).
[0069] Also notable is the data at 17 hours, wherein a very low
amount of DEHA (0.0378 L/m.sup.3) worked about as well as sodium
sulphite (0.38 mg/L dissolved oxygen for DEHA vs. 040 mg/L dissolve
oxygen for sodium sulphite), and that the amount of dissolved
oxygen achieved by 0.0378 kg/m.sup.3 of DEHA was only twice that
achieved by much higher amount (0.17 kg/m.sup.3) of sodium
erythorbate.
[0070] Table 10 presents consolidated comparative data for oxygen
scavengers. Again, the amounts selected are based on cost.
TABLE-US-00010 TABLE 10 30 min 60 min 120 min 960 min Additive
Loading [O.sub.2](mg/L) [O.sub.2](mg/L) [O.sub.2](mg/L)
[O.sub.2](mg/L) Control (30% CaCl.sub.2, with pH -- 4.89 4.86 4.89
4.62 adjusted to 10.0 using NaOH) Sodium Sulphite (uncatalysed) 0.5
kg/m.sup.3 3.43 2.61 1.05 0.4 Sodium Sulphite (uncatalysed, 0.5
kg/m.sup.3 4.75 4.43 3.97 3.6 with 2.5 L/m.sup.3 SC-202) DEHA (with
2.5 L/m.sup.3 SC-202) 0.5 L/m.sup.3 0.25 0.31 0.38 0.21 DEHA 0.126
L/m.sup.3 1.26 0.23 0.19 n/a DEHA 0.0378 L/m.sup.3 2.87 1.64 0.75
n/a Sodium Erythorbate 0.17 kg/m.sup.3 0.45 0.18 0.16 0.19 WOS
(ammonium bisulphate) 0.5 L/m.sup.3 3.2 2.7 2.35 2.75 WOS (ammonium
bisulphate, 0.5 L/m.sup.3 4.08 4.05 3.95 4.15 with 2.5 L/m.sup.3
SC-202) -- Measured at 22 .+-. 1C
[0071] In these data, 0.5 L/m.sup.3 DEHA was more effective than
any other oxygen scavenger at 30 minutes. Beyond this time point,
0.5 L/m.sup.3 DEHA showed oxygen scavenging performance comparable
to sodium erythorbate, even at 960 minutes. At the 60- and
120-minute time points, 0.126 L/m.sup.3 of DEHA performed similarly
to sodium erythorbate.
[0072] 0.0378 L/m.sup.3 of DEHA achieved oxygen reduction at 120
min that was better than much higher amounts of sodium sulphite
(catalyzed and uncatalyzed) and ammonium bisulphate.
[0073] In summary, DEHA is surprisingly effective as an oxygen
scavenger, compatible with other common additives in the fluid, and
also surprisingly effective in brine drilling fluids. These
qualities make it suitable for use as an oxygen scavenger in
drilling fluids, without the need for addition of other oxygen
scavengers.
EXAMPLE
Effects of Antifreezes on DEHA Oxygen Scavenging
[0074] Table 11 presents data from test on impact of antifreezes
methanol and ethanol on the oxygen scavenging activity of DEHA. The
solutions tested as additives were mixes of 30% by volume of DEHA
(an 85% stock solution) with 70% by volume of ethanol (EtOH) or
methanol (MeOH). These were added to the brine, as above, after
aging for 48 hours at -20.degree. C.
TABLE-US-00011 TABLE 11 30 min 60 min 120 min 21 hrs [O.sub.2]
[O.sub.2] [O.sub.2] [O.sub.2] Additive (mg/ Temp (mg Temp (mg/ Temp
(mg/ Temp [L/m.sup.3] L) (.degree. C.) L) (.degree. C.) L)
(.degree. C.) L) (.degree. C.) Control 4.35 22.4 4.41 22.7 4.44
22.8 4.38 21.4 [0.0378] 3.23 22.4 2.42 22.6 1.63 22.7 0.45 21.6
DEHA [0.0378] 3.16 23.0 2.29 24.1 1.15 25.7 0.43 21.3 DEHA in EtOH
[0.0378] 3.17 22.7 2.38 22.9 1.70 23.1 0.40 21.3 DEHA in MeOH
[0075] As may be seen, neither methanol nor ethanol inhibited
oxygen scavenging activity of DEHA. Indeed, DEHA appeared to work
slightly better in ethanol than in its absence.
EXAMPLE 5
Crystallization Points and Stability of DEHA Blends
[0076] Three compositions comprising DEHA and antifreeze were made
to test crystallization and stability characteristics.
[0077] Blend #1: 40% DEHA
[0078] 30% Ethylene Glycol (80/20)
[0079] 30% Water*
[0080] Blend #2: 40% DEHA
[0081] 25% Ethylene Glycol (80/20)
[0082] 35% Water*
[0083] Blend #3: 40% DEHA
[0084] 20% Ethylene Glycol (80/20)
[0085] 40% Water*
[0086] Reverse osmosis (RO) water was used for all three
blends.
[0087] All three blends were mixed in an Erlenmeyer flask, starting
with the RO water and ethylene glycol (EG), and the DEHA was added
last. Each flask was covered with Parafilm, and the blend was mixed
with a stir-bar set to a very low speed, just until the blend was
homogeneous. This was done in order to decrease the exposure to
air, thus helping to minimize the amount of oxygen incorporated
into each blend.
[0088] Monitoring was carried out to ensure that the
DEHA/water/ethylene glycol combination was miscible and stable, and
to check the crystallization point. One desirable goal was to
achieve a very low crystallization point (e.g. -40.degree. C.) and
no phase separation.
[0089] All three blends remained stable at ambient temperature for
the five days they were observed.
[0090] Blends #1 and #2 remained stable at a constant temperature
of -40.degree. C., as well as after having gone through two
freeze/thaw cycles. No phase separation was observed at all, and
the blends remain homogeneous.
[0091] Blend #3 also remained stable overnight at a constant
temperature of -40.degree. C., however there was a small amount of
crystallization observed after being in the -40.degree. C. freezer
over the weekend. However, this amount of crystallization did not
subsequently increase, and in fact disappeared upon subsequent
observation one day later.
[0092] Thus, the concentration of ethylene glycol can be reduced
down to 25% (of an 80/20 mix) and stability is maintained.
[0093] Ethylene glycol can be further reduced to a lower
concentration, in the range of 20-25%, as the blend with 20%
ethylene glycol did remain stable at -40C overnight, and the amount
of crystallization initially observed was quite minimal, and
possibly due to temperature fluctuations.
EXAMPLE 6
AHA and Catalyst Blends
[0094] Testing was conducted on DEHA with one of hydroquinone or
Gallic acid. This testing used a DEHA 85% stock solution at full
strength. The test results set out below show that hydroquinone was
more effective than gallic acid in improving oxygen scavenging in
the base fluid. The formulation with DEHA and just under 1000 ml of
hydroquinone showed a drop in oxygen concentration in 30%
CaCl.sub.2 brine, pH 9-10, from about 5.0 mg/L dissolved oxygen to
0.5 mg/L dissolved oxygen, after 5 minutes when treated with 0.5
L/m.sup.3 concentration of oxygen scavenger, at room temperature.
At 0.05 L/m.sup.3 or higher concentrations of each scavenger
injected into the 30% CaCl.sub.2 brine, reaction rates are very
rapid.
TABLE-US-00012 TABLE 12 O.sub.2 (mg/L) O.sub.2 (mg/L) Time (min)
DEHA (GA) DEHA (HQ) 0 5.01 5.00 5 -- 3.99 20 4.88 3.05 60 4.71 1.90
90 4.62 1.98 120 4.51 -- 150 4.62 --
[0095] Testing was also conducted using methyl ethyl ketoxime
(Mekor 70) in both catalyzed and uncatalyzed solutions. 1 L/m3
Mekor 70 was injected into 30% CaCl.sub.2 at pH of 9-10. 0.05
L/m.sup.3 of Melor 70 catalyzed with 1000 ppm hydroquinone was
injected into 30% CaCl.sub.2, at pH 9-10.
TABLE-US-00013 TABLE 13 Time (min) O.sub.2 (mg/L Mekor 70 O.sub.2
(mg/L) Mekor (HQ) 0 5.11 5.32 5 5.19 5.00 20 5.16 4.79 60 4.92
[0096] Testing with DEHA and hydroquinone used a solution of water
and ethylene glycol as a base fluid and added 30% CaCl.sub.2.
Amounts of DEHA and hydroquinone were tested for their oxygen
scavenging ability and the results set out below.
[0097] Solution Preparation:
[0098] Solution A: 400 g solution of 80:20 (w/w %) of water to
ethylene glycol was prepared using a top load balance (320 g water,
80 g ethylene glycol) .delta.=1.026 g/mL.
[0099] Solution B: 1.5 L of 30% CaCl.sub.2, 575.4 g CaCl.sub.2 in
1500 g water (pH 9-10, .delta.=1.2516 g/mL) was prepared and cooled
to room temperature.
[0100] Solution C: 100g solutions of 5%, 10%, and 15% DEHA in
solution A (w/w %) were created using top loading balance:
[0101] i) 5% solution: 5 g DEHA/95 g solution A;
[0102] ii) 10% solution: 10 g DEHA/90 g solution A;
[0103] iii) 15% solution: 15 g DEHA/85 g solution A.
[0104] Solution D: Using the analytical balance, hydroquinone (Hq)
was weighed and added to 20 g of each batch of solution C, and to
solution A:
[0105] i) 250 ppm Hq in 5% DEHA: 0.0050 g Hq/20 g Solution
C(i);
[0106] ii) 250 ppm Hq in 10% DEHA: 0.0050 g Hq/20 g solution
C(ii);
[0107] iii) 250 ppm Hq in 15% DEHA: 0.0050 g Hq/20 g solution
C(iii);
[0108] iv) 250 ppm Hq (no DEHA): 0.0050 g Hq/20 g solution A;
[0109] v) 125 ppm Hq in 5% DEHA: 0.0025 g Hq/20 g solution
C(i).
[0110] For each trial, 125.16 g (100 mL) of solution B was weighed
out in a 250 mL beaker equipped with a magnetic stirring rod. At a
stir rate of 60 rpm, 150 uL of solution D(i) was introduced using a
micropipette, and a timer was set. After five minutes, the beaker
was removed from the stir plate and the Dissolved Oxygen (DO) was
recorded. This was repeated for solutions D(ii)-D(v). Note: DO
readings, at time=0min, were taken from the stock beaker of
solution B as to avoid altering initial volumes of 100 mL
batches.
TABLE-US-00014 TABLE 14 O.sub.2 O.sub.2 Temp Temp % HQ Initial
Final Initial Final Trail DEHA (ppm) (mg/L) (mg/L) (.degree. C.)
(.degree. C.) 1 0 250 5.24 5.02 21.7 22.4 *2 20 0 5.22 5.23 22.1
21.1 3 5 125 4.92 0.81 23.1 22.6 4 5 250 4.91 0.69 22.9 22.5 5 10
250 4.93 0.58 22 21.9 6 15 250 5.39 0.56 20 19.6 7 15 500 5.23 0.46
21.1 21.2 8 15 750 5.25 0.4 19.4 20 9 15 1000 5.35 0.36 19.2 20.5
10 20 500 5.31 0.42 19.3 20.9 11 20 750 5.42 0.37 19.2 20.6 12 20
1000 5.32 0.32 19.3 20.7 **13 20 1000 5.31 0.31 19.2 21.4
[0111] Note: Trial 2 was 1.5 L/m.sup.3 of O2 ENERSCAV, not included
in sample preparation above. [O.sub.2] final was measured 5 minutes
after scavenger had was added to solution. However readings took
approximately 5 minutes to stabilize. Trial 3 took slightly longer
than the rest of the samples for a stabilized O.sub.2 reading to be
reached. All trials are at 1.5 L/m.sup.3 of scavenger solution.
[0112] **This trial was run at 3 L/m.sup.3. A measurement was also
taken at 120 minutes, 0.37 mg/L reading was recorded. All 20% DEHA
solutions were made using premixed Enerscay.
[0113] In the preceding description, for purposes of explanation,
numerous details are set forth in order to provide a thorough
understanding of the embodiments. However, it will be apparent to
one skilled in the art that these specific details are not
required. The above-described embodiments are intended to be
examples only. Alterations, modifications and variations can be
effected to the particular embodiments by those of skill in the art
without departing from the scope, which is defined solely by the
claims appended hereto.
[0114] All references cited herein are incorporated by reference in
their entirety.
* * * * *